In this type of boot, the initial position of the locking lever corresponds to an initial adjustable forward-extension reference position, from which the upper can pivot angularly in relation to the shell base by a predetermined amplitude.
To this end, European Patent Application No. 0 286 586 discloses forward extension-adjustment means consisting in positioning an adjustable linkage device between a rear portion of the upper and an intermediate swivelling cover carrying, moreover, the rocker which, in its turn, cooperates with the shell base, in accordance with the aforementioned criteria.
This device complicates the manufacture of the boot, since it requires the use of an additional element, i.e., the pivoting cover.
French Patent Application No. 2 647 649 attempts to solve this problem by proposing a solution involving forward extension adjustment, by making either the length of the rocker arm or the relative position of the stop variable.
This, however, requires the production of additional parts and, in consequence, extends the time required for boot-assembly.
In other words, while this last-mentioned device solves one problem, it creates another.
Furthermore, when the length of the rocker arm is made variable, its reliability in the locked position becomes uncertain, given that it bears extremely strong compression/buckling forces.